I'm currently using Lightroom CC2015.4 (latest version as of writing this discussion) and Lightroom Mobile is trying to sync 8 photos and will not complete the sync. It's been like this for quite a long time and isn't really a huge problem but it's getting annoying to see the "Syncing 8 photos" at the top left of my Lightroom on my Mac. Is there any way to find out what these 8 photos are and can I abort their sync or an I just stuck with these? Anything else I sync with Lightroom Mobile works just fine and when they finish, I still have those same 8 photos syncing. Can anyone help?

I don't know what causes this, but I solved it for myself by wiping the slate clean by going into Lightroom>Preferences, and on the Lightroom mobile tab, clicking on Delete All Data. Lightroom then re-syncs all the collections you have set to sync.